Cake discharger mechanism



CAKE DISCHARGER MECHANISM Filed May 22, 1940 INVENTOR l ATTO R N EYPatented Apr. 24, 1945 2,374,363 CAKE DISCHARGER MECHANISM Jasper A.McCaskell, Los Angeles, Calif., assignor to McCaskell Filters, Inc.,

Los Angeles, Calif.,

` a corporation of California Application May 22, 1940, Serial No.336,503

('Cl. 21o-194) Claims.

'This invention relates to pressure lters capable of continuousoperation and, more particularly, to a mechanism for discharging filtercake therefrom.

Simple tapered nozzles, of the type described in my prior Patent No.1,784,372, have in many cases proven adequate in the compacting anddischarging of filter cake Without permitting the escape of pressureiiuid from the lter. In some cases, however, Where the cake itself doesnot oii'er sufllcient resistance to discharge, it has been foundnecessary to modify this structure by providing it with a valve. Theconstant resistance type valve controlled nozzle modification which hasheretofore been used is also described in the same patent. This modiedstructure is particularly suitable for use in the discharge of slimy ortalcy cake.

In some cases, however, when a, cake has either a highly siliciousnature or consists of coarse grained salts, its resistance to dischargeincreases at unexpected moments and to an unexpected degree. In thenormal course of operation this type of cake may discharge freely forhours and then suddenly its resistance to discharge will increase. Ifthe total resistance to discharge, that is, the resistance of the cakeitself, plus the resistance offered by the valve, is not relieved in onemanner or another, the horse power of the driving motor will in suchcases increase sufciently to kick out the overload relays and stop theoperation of the entire filter press.

not only annoying but also result in temporary disruption of the plantprocess, etc.

One of the objects of this invention is to provide means forcontinuously removing filter cake of a highly silicious nature from thefilter pressy without fear of building up sufficient resistance to stopthe operation of the filter press.

Another object of this invention is to provide means to keep the totalresistance to lter cake discharge within certain predetermined limits.

A still further object of this invention is to provide automatic meansfor decreasing the total resistance to filter cake discharge, when suchresistance exceeds a predetermined limit.

Another object of this invention is to provide eiilcient continuousfilter cake discharge means for pressure filters.

I have found that the total resistance to iilter cake discharge introlled and kept within a such discharge. I have further found thatcontrolling means of this type may be made automatic by providing meansoperable by the variation in resistance to discharge to inversely changethe degree of resistance offered by the discharge valve. 'I'his may beaccomplished by a combination of means coacting with one another toproduce the desired results. For example, means may be provided,operable by a change in the resistance to filter cake discharge, toinversely change the resistance oiiered by the discharge valve to thedischarge of lter cake.

In the accompanying drawing, which illustrates one form of constructionembodying features of my invention: I

Figure 1 is a vertical elevation, partly in section, of a lter press),the discharge mechanism, and means to control the operation of thedischarge mechanism;

Figure 2 is a vertical section of an electrically operateddiaphragm-type valve; and

Figure 3 is a vertical section through the valve takensubstantiallyatright angles 'to the section of Figure 2.

The discharge mechanism of my invention includes in general a dischargenozzle, means for compressing and conveying lter cake toward thedischarge nozzle, a discharge valve constructed to offer varying degreesof resistance to filter cake discharge through the nozzle, and

means to inversely vary the resistance offeredA by the discharge valveas the total resistance to the discharge of the filter cake increasesorde- Referring more specifically to the drawing, the' lter I0 which is ofthe continuous pressure type, is composed of a casing or housing II, inwhich a series of illter elements, or leaves I2, is'mounted on a hollowrotatable shaft I3 through which the filtrate is drawn omv Sludge lisadmitted to the inside of the casing and pressure to force the filtratethrough the ltering medium and out the hollow shaft I3. The now of thefiltrate through the filter disks or leaves deposits a cake which iscontinuously scraped olf by scrapers located in the lower portion of thefilter and dropped into cake hopper I4.

A lter press of this type is' described in greater detail in my priorPatent No. 1,266,133.

In order to make continuous operation of the filter possible, it isnecessary to include in the construction of the filter, means forremoving the filter cake scraped from the leaves or disks I2 withoutpermitting the escape ofthe pressure.

medium. In the specific embodiment illustrated is then put underI ation.

valve in Figure 1 of the drawing, this is accomplished by the coactionoi the worm Il, the discharge e nozzle Il and discharge valve Iii. Theillter cake which has been scraped from the filter leaves I2 and droppedinto hopper Il is directed into the opening 2l in the cylindrical casing22 where the revolving worm I6 conveys the filterscake toward dischargenozzle I8, while compressing it to squeeze out the fluid which escapesfrom the cylinder through holes 24. The tightly compressed cake whichforms in the nozzle Il, the space II between the discharge valve 30, andthe threads of the worm Il acts as a seal which prevents the air andfluid under pressure in the filter from escaping while the solid cakemay be continu-y ously discharged.

The discharge valve 3l, the counter pressure of which prevents a tooeasy discharge of illter cake and a loss of pressure in the illter, isprovided with means for varying the pressure exerted by it upon thefilter cake being discharged. This is accomplished in the illustrativeexample of such means shown in Figure 1, by a discharge valve cylinder$2 and piston u rigidly connected with the discharge valve by piston rodSi. Any variation in pressure in the cylinder l2 will directly anect thepressure on the piston 3| and, therefore, atleet resistance offered bythe valve Il against the discharge of filter cake.

The pressure existing in the discharge cylinder may be controlled in anydesirable manner. For example, the discharge cylinder 32 may beconnected with a pressure source by a supply line lil, pressure controlvalve 42 and supply line 4i.

A fourway valve lla conveys the pressure fluid through the branch b tothe left side of the piston 34 at all times when the filter is in oper-When it is desired to withdraw the valve 3l from the discharge nozzle Ilto permit inspection or repair, the valve 40a is turned by applying awrench or tool to the squared end thereof to cause the air to flowthrough the branch c to the right side of piston Il and to vent thebranch Mb through the vent port Ild.

Although it is not essential that the control valve be electricallyoperated, I make use of an electrically operated three-way valve inpreferred embodiments of my invention. The speciilc embodiment of thecontrol valve l2 illustrated is a four-way diaphragm type valve, oneoutlet of which is closed with a plug M. The specic type of valveillustrated is tric Co. and designated in Circular GEA-2323A as Threeorfour-way diaphragm-type valve, CR950'l-F1C or valves may be used. Thevalve illustrated is operated by a solenoid contained in the top o! thehousing. When the'cirouit operating the valve is closed, the coil isenergized and the core rises upward, thus lifting the stem of the pilot41 and opening the pilot valve I1. This permits the pressure material.normally compressed air, to flow from4 the. line Il through the channelIla into the diaphragm chamber where its pressure is exerted-,againstthe large diaphragm The diaphragm. which requires very little pressuredifferential for its operation, produces a positive movement in forcingthe main valve down against the pressure of spring I! as pressure in thechamber builds up. When this occurs the air in the line l-lb andcylinder 32 is permitted to exhaust gradually through the valve 42 andneedle valve 43 which is partially open, to thus gradually reduce thepressure in the cylinder 32 and decrease the resistance to made by theGeneral Elec- FlD" although other types of l il ' connection between the-charge is reduced the I specific embodiments cake discharge. As theresistance to cake diseurrent in the power line Il to the motor Ildecreases and this causes the current tothe solenoid l. to be cut 0H.When the current is stopped, the pilot valve l1 drops into position andpressure against the diaphragm is removed, allowing spring Il to forcethe main valve shut. An adjustable metering pin Il in the discharge linella from the diaphragm chamber makes possible an adjustable time relayin closing. This valve is normally connected in the circuit in suchmanner that there is a free passage from the source of pressure supply4| through the valve tothe pressure line Il-llb leading to .thedischarge cylinder 32 when no current is being supplied to the circuit.When current is supplied, the pressure line Il-llb leading to thecylinder 32 is in direct communication with the third opening in thevalve a which leads to a needle valve 43 left partly open, thuspermitting pressure material to escape therethrough and decrease thepressure in the system gradually.

` When an electrically operated valve of the type described above isused as the means to control the pressure existing in the dischargevalve cylinder and thereby control the pressure of the discharge valveagainst the discharging filter cake, the pressure exerted by the valvecan be made to vary inversely with the resistance to filter cakedischarge. This can be accomplished by providing a switch in theelectrically operated valve circuit, which will turn on the current inthe circuit when the total resistance to filter cake discharge exceeds a.predetermined value and turn oil the current when the resistance dropsto any predetermined value. In the particular embodiment i1lustrated inthe drawing this is accomplished by passing the power line 5I to themotor il through a current transformer S2 which is wired to a snapaction relay 54. The snap action relay is wired to the electricallyoperated valve and controls its action. The snap action relay is soadjusted that, under normal operating conditions, it opens the circuitthrough the lines l! and 59 and the solenoid operated valve 42, thusie-energizing the valve and permitting a direct pressure supply line 4Iand the line lll-40h leading to the filter cake discharge cylinder 32.However', rent in the power line I3 increases beyond a certainpredetermined limit, the snap action relay is set to close the circuitin lines il and il. The closing of the circuit will supply electricalenergy to the solenoid 46 and will cause the valve 41 to close the portbetween the pressure supply pipe 4i and line 4l and open the portbetween the line I0 and the line provided with the needle valve 43through which the excess pressure in cylinder 32 can bleed outgradually.

The combination of means described above, of which are illustrated inthe drawing, is adaptable for controlling and keeping the totalresistance to filter cake discharge'within specified limits and thusinsures the continuous operation of the illter press, even when thefilter cake is oi a highly silicious nature. These means cooperate withone another as follows:

After the filter cake has been scraped from the illter leaves of thepress and dropped into hopper Il, it is directed into the dischargecylinder where the screw conveyor l0 conveys it toward, and compressesit in, the discharge nozzle il and against discharge valve 30. In thenorwhen the curmal course of operation, the screw conveyor will exert asuiicient pressure on the lter cake to overcome both the resistance todischarge offered by the lter cake itsell and the resistance offered bythe valve 30, thus permitting the cake to be discharged freely. However,if the total resistance to discharge suddenly builds up for someunexpected reason, the resistance to discharge will increase the powernecessary to turn the screw I6. Since this screw is turned by motor 5I,the increase in resistance will require an additional supply of power tothe motor. As the horse power of the motor varies in proportion to theamount of current passing through the power line 53, any increase inpower will increase the electric current in the power line 53. Theincrease in current will be transmitted to the snap action relay 54through the current transformer 52, and will. if the current issufllcient, make the circuit by means of which the solenoid of controlvalve 42 is actuated. thereby changing the setting of the valve 42 andgradually reducing the pressure in the cylinder 32. When the resistanceto cake discharge has decreased suiliciently to lower the power neededto drive the motor 5i, the snap action relay 54 will snap back to theposition which opens the circuit to the solenoid 46. When the coil ofthe solenoid is no longer energized. the pilot valve will close. thepressure on the diaphragm 48 will be relieved and the spring on thebottom of the valve will open the port between the pressure supply lines4I and 40 and close the port leading to the partly open needle valve 43.This will permit the pressure existing in the discharge cylinder 32 toincrease to that normal in the supply line 4|. The total resistance todischarge will, therefore, decrease in proportion to the decrease inpressure of the valve 30 against the filter cake and increase whenconditions are restored to normal.

It will be understood that the specific embodiment illustrated in thedrawing and described in the specification is given by way ofillustration and not as limitation of the discharger mechanism of myinvention, and I, therefore, desire a broad interpretation of theinvention within the scope and spirit thereof and limited only by theclaims appended hereinafter.

I claim: i

1. In combination with a pressure lter a discharge screw for dischargingthe lter cake, a motor for driving the discharge screw, a dischargevalve for controlling the discharge of lter cake from the ltercomprising a valve seat, a conical valve adapted to seat upon the valveseat and control the discharge of filter cake from the lter press, avalve stem carrying said valve, a piston connected to said valve stemand a iluid pressure cylinder in which the piston is mounted forreciprocation, a means for controlling the pressure in said cylinder bywhich the valve is pushed toward its seat, including a fluid pressuresupply line normally in communication with said fluid pressure cylinderto urge said valve toward its seat, an electrically controlled valve insaid fluid pressure supply line normally in pressure communicatingposition, electrically operated means for controlling said latter valve,a pressure discharge line from said electrically controlled valve and anadjustable needle valve in said discharge line for controlling the rateof discharge of pressure from said cylinder, and an electric circuit tosaid motor and to said electrically operated means and a relay in saidcircuit controlled by variations in the current relill quirements ofsaid motor to shit t said electrically controlled valve from pressuresupplying to pressure discharging position to permit the escape of fluidfrom said fluid pressure cylinder.

2, In combination with a pressure lter a cake discharger comprising asubstantially cylindrical casing, a screw conveyor for dischargingfilter cake rotatable therein, means to rotate said c onveyor, a valveseat through which filter cake is discharged, a discharge valve seatingon said valve seat to control discharge therethrough, fluid pressuremeans for actuating said discharge valve toward said valve seat, relaymeans actuated by an increase or decrease in the current ,transmitted tothe conveyor rotating means to change the fluid pressure of said uidpressure means inversely and proportionately to variations in currenttransmitted to the conveyor rotating means, said pressure changing meansincluding a pressure line for conveying the iluid pressure for actuatingthe discharge valve toward its seat, a valve in said pressure line,means operable from the relay to change the setting of said pressureline valve from pressure supplying to pressure discharging positionresponsive to variations in the current transmitted to the conveyorrotating means and means to regulate the rate of the discharge ofpressure fluid from the rear of the discharge valve when the pressureline valve is in discharging position.

3. In combination with a pressure lter. a cake discharger comprising, asubstantially cylindrical casing, a screw conveyor for discharging ltercake rotatably mounted therein, a valve seat through which the lltercake is discharged, a fluid pressure actuated discharge valve seating onsaid valve seat, electrical means for rotating said screw conveyor, andmeans connected to the electrical means and actuated upon variation incurrent in said electrical means for varying the pressure actuating saiddischarge valve, said means .including a pressure supply line forsupplying pressure to urge said discharge valve toward its seat, anelectrically operated valve in said pressure supply line, and a relay tochange the setting of said electrically operated valve from pressuresupplyingto pressure discharging position when the current requirementsfor rotating said screw conveyor go up, and a pilot valve for regulatingthe rate of fluid pressure discharge when said electrically controlledvalve is in pressure discharging position.

4. In combination with a pressure filter, a cake discharger comprising,a substantially cylindrical casing, a screw conveyor for discharginglter cake rotatably mounted therein, a valve seat through which the ltercake is discharged, a fluid pressure actuated discharge valve seating onsaid valve seat, electrical means for rotating said screw conveyor, andmeans connected to the electrical means and actuated upon variation lncurrent in said electrical means for varying the pressure actuating saiddischarge valve, said means including a pressure supply line forsupplying pressure to urge said discharge valve toward its seat, anelectrically operated valve in said pressure supply line, and a relay tochange the setting of said electrically operated valve from pressuresupplying to pressure discharging position when the current requirementsfor rotating said screw conveyor go up, a needle valve for regulatingthe rate of pressure discharge when said electrically controlled valveis in pressure discharging position, and spring means adapted to restorethe electrically operated valve to pressure supplying position.

5. In combination with a pressure filter, a motor. a discharge screw fordischarging filter cake driven by said motor, a discharge valve forfilter cake comprising a valve seat, a conical valve disposed adjacentsaid valve seat to seat thereon and control the discharge of filter cakefrom the filter press, a valve stem carrying said valve and slidablymounted in a uid pressure cylinder and connected to a piston in saidcylinder, and means for controlling the pressure in said cylinderincluding a fluid pressure supply line, normally communicating with saidfluid pressure cylinder to press said valve toward its seat, anelectrically controlled valve, a discharge line from said electricallycontrolled valve, and an adjustable needle valve in said discharge linefor varying and controlling the iluid pressure in said cylinder wherebysaid conical discharge valve is yieldlngly pressed against said valveseat at a predetermined pressure, an electrical circuit to said motorand to said electrically controlled valve, and means in said circuit forshifting said electrically controlled valve to change the pressure onsaid piston in said circuit. v

JASPER A. MCCASKELL.

